*UPDATE* - It appears as though any issues have been resolved now.
As much as I hate to write this one up seeing how it feels a lot like Déjà vu, there's been several reports now from Android and iOS users that BBM is experiencing some issues. It doesn't appear to be widespread but rather a bit regional this time around with folks in the UK experiencing it more so than others. To go along with the reports of it being down though, we've also heard there is a good chance it's maintenance for the upcoming release of BBM 2.0.
However, if that is the case I think BlackBerry should give folks a heads up, they do have a pretty massive following on their Twitter account to warn folks of such things. Transparency is better than letting people wonder. In any event, sound off in the comments if you're having issues with your BBM right now. We'll update accordingly when we hear more.